Abstract Sudden cardiac arrest is a major public health problem, afflicting over 535,000 persons in North America each year with dismal event survival rates near 10%. There is currently no medicinal intervention demonstrated to have a beneficial effect on post-arrest outcome with targeted temperature management arguably being the only intervention known to potentially improve post-cardiac arrest brain injury and survival. Thus, new therapies aimed at reducing the mortality and morbidity in post-cardiac arrest patients are essential. Thiamine is an essential co-factor of pyruvate dehydrogenase (PDH), the enzyme responsible for the conversion of pyruvate into acetyl-CoA and entry into the Krebs Cycle (aerobic metabolism). Previous investigators have found that post-arrest patients exhibit ?venous hyperoxia? or ?luxurious perfusion? ? the systemic and cerebral inhibition of oxygen consumption despite the presence of adequate oxygen delivery. Our preliminary data confirms the finding of depressed cellular oxygen consumption and puts forth the novel data that this depression can be overcome with the administration of in vitro thiamine as demonstrated by improved mortality and neurological morbidity in a mouse model of cardiac arrest. In a murine model of cardiac arrest, we found that intravenous thiamine increased PDH activity, improved cerebral oxygen consumption, mitigated histological injury to various areas of the brain, improved survival, and improved good neurological outcome. While our murine model suggests thiamine may be effective independent of deficiency, we did additionally find that upwards of 44% of post-arrest patients were thiamine deficient similar to rates in septic shock. Based on these data, we hypothesize that the administration of thiamine in post-cardiac arrest patients will mitigate lactic acidosis, improve cellular oxygen consumption, and improve clinical outcome. To test this hypothesis, we will perform a prospective, Phase II randomized pilot study providing thiamine versus placebo for post-cardiac arrest patients. Our primary endpoint will be attenuation of lactic acidosis in the thiamine group as compared to the placebo arm. Lactate serves not only as a surrogate for mortality but also as a parameter that would be directly modified by thiamine. Our secondary endpoints will include determination of whether thiamine will improve cellular oxygen consumption, increase PDH activity, attenuate biomarkers indicative of neurological injury, and improve clinical endpoints of neurological injury and organ-injury. The long-term goal of this line of research is to evaluate thiamine as an adjunctive therapy for post-cardiac arrest patients. Thiamine is safe, inexpensive, and easily administered ? thus, if our hypothesis is proven true and future research proves efficacy, adoption of this adjunctive therapy is feasible and significant.